(1) Field of the Invention
The present invention is related to providing a heterogeneous traffic Connection Admission Control system for Asynchronous Transfer Mode (ATM) networks and a method thereof, for dynamically controlling a system capacity to a delay demand bound of a heterogeneous traffic class in order to meet the cell loss rate for a user""s demand, reduce the influence of mutual traffic interferences and enable the Connection Admission Control to function in a real time.
(2) Description of the Related Art
An ATM network for realizing the broadband network such as a Broadband- Integrated Digital Service Network (B-ISDN) can generally provide a multimedia service of various traffic characteristics, including data, voice and image. The ATM network is supposed to control the traffic input thereof in order to service such a variety of signals as a voice sensitive to delay and a video sensitive to the cell loss respectively. The main aim of the operation of the communication network is to handle problems of an acceptable bound exceeding the network capacity , a partial loss and failure of the network by maximizing the network efficiency . The ATM network is provided with an efficient network controller to control a traffic network, effectively, even if the exact characteristics of traffic signal sources are unknown and/or the Quality-Of-Service is changed according to the elapse of time.
Generally, a Connection Admission Control (CAC) means serial actions to determine whether a Virtual Channel Connection (VCC) or a Virtual Path Connection (VPC) has obtained approval to have a connection at a call establishing phase or a renegotiation phase of call. The connection admission control is a software function to determine whether an ATM switch allows or rejects the connection demand. The connection demand is defined as a source traffic parameter and a requested Quality-of-Service (QOS) degree. In order to operate the Connection Admission Control, there are methods using an equivalent bandwidth, a burst model and a traffic measurement.
The equivalent bandwidth method comprises steps for approximating a bit rate generated at a multi-connection with a fluid-flow model, calculating the equivalent bandwidth of respective calls and determining whether the connection is admitted after checking if the equivalent bandwidth exceeds the residue bandwidth of the connection demand call. The burst model method is for controlling the connection admission using only a maximum bit rate and an average bit rate irrespective of the on-off regional distribution of a cell reaching process.
Referring to FIG. 1, a conventional Connection Admission Control system in an ATM network has an acceptable connection admission as follows:
One subscriber terminal 1 reports the Quality-Of-Service degree representing a traffic descriptor, a cell transmission delay and a cell loss rate to the ATM network 3 in the form of a signal message. A Connection Admission Control portion 2 checks the information reported and current load status in the ATM network 3 and then determines whether or not a new connection admission is acceptable. Herein, the traffic descriptor means the description of all traffic characteristics such as the maximum cell rate, the average cell rate, the burstiness and the shapes of signal resources (voice, image).
On the other hand, when the new connection admission is accepted as a result of the decision of its request, the Connection Admission Control portion 2 informs the connection admission to the subscriber terminal 1 and the ATM network 3 so that the subscriber terminal 1 is connected to the ATM network 3. The ATM network 3 includes a multiplexer/reverse-multiplexer 3a for multiplexing a signal from the subscriber terminal 1, reverse-multiplexing data transferred from another subscriber terminal 4 and transferring reverse-multiplexed data to the subscriber terminal 1; a multiplexer/reverse-multiplexer 3b for multiplexing data from the other subscriber terminal 4, reverse-multiplexing data transferred from the one terminal 1 and transferring reverse-multiplexed data, to the other subscriber terminal 4; public switches 3c and 3d for performing mutual data transmissions between the multiplexer/reverse-multiplexers 3a and 3b. Therefore, when the Connection Admission Control portion 2 allows the connection admission to the subscriber terminal 1, data from the subscriber terminal 1 is multiplexed and reverse-multiplexed at the multiplexer/reverse-multiplexer in turn and then transferred to the other subscriber terminal 4, while data from the other subscriber terminal A is multiplexed and reverse-multiplexed at the multiplexer/reverse-multiplexer in turn and then transferred to the one subscriber terminal 1, thereby performing the mutual communication between terminals. The Connection Admission Control system also controls the connection admission using methods of an equivalent band width, a burst model and traffic measurements.
But, the Connection Admission Control method using the equivalent bandwidth has difficulty in calculating the exact equivalent bandwidth of an individual call in advance. The Connection Admission Control method using the traffic measurement has a problem in reducing the link use efficiency if the number of the traffic class is greater or lesser. The Connection Admission Control method using the burst model is simple because of controlling a connection admission using only a maximum bit rate and an average bit rate irrespective of the on-off regional distribution of a cell reaching process, but it has a problem in that the calculation of the maximum bit rate and average bit rate becomes complex under the heterogeneous traffic environment.
In order to resolve these problems and overcome these disadvantages, an object of the invention is to provide a heterogeneous traffic Connection Admission Control system in ATM networks for dynamically controlling a system is capacity to a delay demand bound of a heterogeneous traffic class in order to meet a cell loss rate for an user""s demand, reduce the influence of mutual traffic interferences and enable the Connection Admission Control in a real time.
The other object of the invention is to provide a heterogeneous traffic Connection Admission Control method in ATM networks for dynamically controlling a system is capacity to a delay demand bound of a heterogeneous traffic class in order to meet a cell loss rate for an user""s demand, reduce the influence of mutual traffic interferences and enable the Connection Admission Control in a real time.
According to the invention, a heterogeneous traffic Connection Admission Control system in ATM networks comprises: a Connection Admission Control means for determining whether the connection admission is acceptable based on a maximum cell rate obtained by the combination of equivalent bandwidths calculated by each of a Connection Admission Controller upon the connection request of calls input into respective connection node; a bandwidth allotting means for determining a service capacity of each class in proportion of the equivalent bandwidth of each traffic class to the summing up of all traffic classes inputted into the Connection Admission Control means; means for temporally storing ATM cells through the Connection Admission Control means; and a server for fetching the ATM cell of each class from the storing means and transferring it through a transferring channel.
Also, a heterogeneous traffic Connection Admission Control method in ATM networks comprises steps of calculating an equivalent band width of each traffic class using a distribution function of the number of cells estimated through the traffic measurement of each class; determining the capacity of a transferring channel in proportion to the calculated equivalent bandwidth upon the connection request of a new call; and comparing the link capacity determined above with the results of summing up the maximum cell rate of the call requesting the new call to the equivalent bandwidth of all classes.